1. Field
The subject matter disclosed herein relates to electronic devices, and more particularly to methods and apparatuses for use in and/or with a device capable of receiving satellite positioning systems (SPS) signals.
2. Information
Wireless communication systems are fast becoming one of the most prevalent technologies in the digital information arena. Satellite and cellular telephone services and other like wireless communication networks may already span the entire globe. Additionally, new wireless systems (e.g., networks) of various types and sizes are added each day to provide connectivity among a plethora of devices, both fixed and portable. Many of these wireless systems are coupled together through other communication systems and resources to promote even more communication and sharing of information.
Another popular and increasingly important wireless technology includes navigation systems and in particular satellite positioning systems (SPS) such as, for example, the global positioning system (GPS) and other like Global Navigation Satellite Systems (GNSS). SPS enabled devices, for example, may receive wireless SPS signals that are transmitted by orbiting satellites of a GNSS and/or other terrestrial based transmitting devices. The received SPS signals may, for example, be processed to determine a corresponding GNSS system time, a range or pseudorange, an approximate or accurate geographical location, altitude, and/or speed of the SPS enabled device. Consequently, various position and/or velocity estimation processes may be supported, at least in part, using an SPS enabled device.
Certain devices may be enabled to receive and process SPS signals transmitted by two or more GNSS. For example, certain devices may include one or more SPS receivers capable of receiving SPS signals from GPS and one or more other GNSS, such as, e.g., Galileo or GLONASS. Each GNSS has a specific corresponding ‘system time’, which is communicated through the SPS signals to receiving devices. For example, GPS and GLONASS transmit respective system time information through navigation messages that are periodically transmitted via the SPS signals. An SPS receiver may then decode one or more navigation messages, as needed, to access the system time information and determine the system time for the applicable GNSS. In certain situations, a significant period of time may be required, e.g., on start-up, to determine a system time for one or more GNSS or other like navigation systems. This tends to increase the time-to-fix an estimated position as well. Hence, it may be useful to provide methods and apparatuses that may reduce the period of time spent determining system time(s) for one or more navigation systems in an SPS.